Silicone polymers have many unique properties, including wide service temperature range; low viscosity change vs. temperature; low flammability; shear stability; chemical inertness; oxidative stability; UV stability; low toxicity; and the like. These and other properties have facilitated the adoption of silicon polymers as dielectric, hydraulic, heat transfer, power transmission and clamping fluids. Silicon polymers have also found applications as additives incorporated into plastics and rubbers as process and release aids, into coatings for flow and level control and into process streams as antifoams. Other unique properties have led to their introduction in acoustical applications such as ultrasonic sensor and sonar buoys. This proliferation of applications has engendered many improvements and refinements of silicone polymers.
Anionic polymerization of cyclosiloxanes, particularly hexamethylcyclotrisiloxane (D.sub.3) and octamethyltetrasiloxane (D.sub.4), has been reported previously. It is known that D.sub.3 polymerization does not occur in hydrocarbon solvents. See C. L. Frye, R. M. Salinger, F. W. Fearon, J. M. Klosowski and T. deYoung, J. Org. Chem., 35, 1308 (1970). Although the anionic species was formed (Bu-Si(CH.sub.3).sub.2)--O--Li.sup.+), it did not polymerize. Addition of a polar promoter, such as THF, diglyme, or DME, then stimulated the polymerization. See J. M. Yu, D. Teyssie, R. B. Khalife and S. Boileau, Polymer bulletin, 32, 35-40 (1994). The resultant polymer anion PDMS--O--Li .sup.+ can then be protonated to afford PDMS--OH, capped with a silicon halide (R.sup.3 R.sup.4 R.sup.5 --Si--X) to afford PDMS--O--SiR.sup.3 R.sup.4 R.sup.5, or coupled with suitable coupling agents (SiCl.sub.4, Me.sub.2 SiCl.sub.2, HSi(OMe).sub.3) to afford (PDMS).sub.n, where n=number of coupling agent functionalities. In spite of considerable synthetic efforts, however, there are few good ways to affix functionality to the termini of the silicone polymers.
Conventional hydrocarbon-based polymers generally lack mechanisms for bringing about crosslinking via low-temperature or ambient temperature cure (e.g., moisture cure or addition-cure). Such cure pathways are known in the case of siloxane polymers, and the development of such facile cure mechanisms for organic systems is highly desirable. Unfunctionalized hydrocarbon/silicone block copolymers have been prepared by anionic techniques, as described in U.S. Pat. No. 5,618,903, Makromol. Chem., 176, 1641 (1975), and Macromolecules, 29, 3397 (1996). Symmetrical homotelechelic functionalized block copolymers were also prepared anionically, as detailed in U.S. Pat. No. 5,561,210.